58 Biology of Micro-organisms 



There are also several bacteria which produce the acetic fermenta- 

 tion, though it is generally attributed to Bacillus aceticus. There 

 are two equations to express this fermentation: 



I. CH2CH2OH -I- = CH3CHO -1- H2O 



Alcohol Oxygen Aldehyd Water 



11. CH3CHO + O = CH3COOH 



Aldehyd Oxygen Acetic acid 



A number of different bacilli seem capable of converting milk-sugar 

 into lactic acid, though Bacillus acidi lactici is the best known and 

 most active acid producer. The butyric fermentation generally due 

 to Bacillus butyricus may also be caused by other bacilli. (For an 

 exact description of the chemistry of the fermentations reference 

 must be made to special text-books. *) The lactic acid and butyric 

 acid fermentation, have the following equations: 



I. C12H22O11 +H2O = C6H12O2 + CeHijOe 



Lactose or milk sugar Galactose Dextrose 



II. CeHuOe = 2C3H6O3 



Galactose Lactic acid 



III. C6H,206 = C4H8O2 + CO2 + 2H2 



Galactose Butyric acid 



Putrefaction. — Putrefaction is a catalysis of proteins resulting 

 from the activity of micro-organismal catalysts or enzymes. It is 

 associated with the evolution of a vile odor. The first step in the 

 process seems to be the transformation of the albumins into peptones, 

 then the splitting up of the peptones into gases, amino-acids, bases, 

 and salts. In the process innocuous albumins are frequently 

 changed to toxalbumins, and sometimes to peculiar putrefactive 

 alkaloids known as ptomains. 



Vaughan and Novy define a ptomain as "a chemical compound, 

 basic in character, formed by the action of bacteria on organic matter." 

 The chemistry of these bodies is very complex, and for a satisfac- 

 tory description of them Vaughan and Novy's bookf is excellent. 



Ptomains probably play but a small part in pathologic conditions. 

 They are formed almost exclusively outside of the living body, and 

 only become a source of danger when ingested with the food. It is 

 supposed that cases of ice-cream and cheese poisoning are usually 

 due to tyrotoxicon, a ptomain produced by the putrefaction of the 

 protein substances of the milk before it is frozen into ice-cream or 

 made into cheese. The safeguard is to freeze the milk only when 

 perfectly fresh and avoid mixing the milk, cream, sugar, and flavor- 

 ing substances, and allowing the mixture to stand for some time 

 beforehand. 



* See "Enzymes and Their Applications," by Jean EfEront, translated by 

 S. C. Prescott, New York, 1902; "Micro-organisms and Fermentation," by 

 Alfred Jorgensen, translated by A. K. Miller and A. E. Lennholm, London, 

 1900; and the many writings of Christian Hansen. 



t "Ptomaines and Leucomaines," 1888; "Cellular Toxins," 1902. 



